A device for the photometric measurement of samples is generally disclosed within U.S. Pat. No. 7,102,131 to Spolaczyk et al. Samples within individual sample wells are exposed to radiation from a single light source or a series of light sources and the light modified by the samples, for example fluorescence light, is intercepted by an optical device and is guided to a section of at least one sensor for measuring the intensity and evaluation thereof in an evaluation device arranged downstream of the sensor. The light source(s) are controlled individually by a control device, and the evaluation device and the control device are controlled such that the evaluation device can separate the light from each sample from the light of the other samples. The position of the sample upon, for example, a thermocycler that supports the sample determines the exact position where light modified by the samples shines on the sensor. Small shifts in the position of the sample will slightly shift the area on the face of the sensor where the light from the sample shines.
The inventors of the present invention, through testing have determined that the sensor inherently has different sensitivity levels across its face. Additionally, the sensor is subject to the effect of intensity drift over time. Also, the magnitude of intensity drift varies across the face of the sensor. As a result of these three factors, when the position on the sensor where light from the sample shines changes, measurement results can be difficult to reproduce with good precision. Additionally, if the brightness of the light is not consistent across the section of the sensor upon which the light shines, measurement results are difficult to reproduce. Variations in brightness may be caused by the variations in position of the sample material in sample wells.
It is possible to take the different sensitivity of the sensor area into consideration for every location of the specimens by calibration and determining correction factors, and calculating corrected measurement results with the correction factors. This is a time consuming process and also cannot be used for correcting intensity drift.
What is desired is a way to quickly and easily increase the homogeneity of the sensing qualities of the sensor and as a result improve the precision and reproduceability of measurements recorded from tested samples.